This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-71128, filed Mar. 14, 2000; and No. 2001-34391, filed Feb. 9, 2001, the entire contents of both of which are incorporated herein by reference.
The present invention relates to a scanning microscope or a scanning unit to which a technique of a scanning microscope is applied and which is used in an apparatus for observing or processing a sample or for recording information. More particularly, the present invention relates to a scanning microscope using this scanning unit.
A stage mechanism for causing translational movement or rotational movement of an object is one of the basic elements of a machine mechanism. Further, an automatic stage capable of controlling stage movement by using a drive mechanism such as a motor in accordance with a control signal such as an electrical signal is used in every scene.
A machine mechanism for repeatedly causing reciprocating translational movement or forward or backward rotational movement of an object in a relatively short period of time is also referred to as a scanning unit. Here, such a machine mechanism will be simply referred to as a scanning unit unless otherwise specified.
Such a scanning unit is mounted in, for example, a scanning microscope. As a scanning microscope apparatus in which such a scanning unit is mounted, there are a scanning probe microscope, a later scanning microscope, or an electronic scanning microscope which is of a type capable of obtaining an image by scanning a sample with an electronic beam being fixed.
A scanning probe microscope (SPM) is a scanning microscope which mechanically scans a mechanical probe to obtain information of a sample surface, and includes a scanning tunneling microscope (STM), an atom force microscope (AFM), a scanning magnetic force microscope (MFM), a scanning electric capacity microscope (ScaM), a scanning near-field optical microscope (SNOM), a scanning thermal microscope (SThM) and others. In recent years, a nano-indentator and the like, which makes an indentation by pressing a probe made of diamond against a sample surface and checks hardness and the like of the sample by analyzing how the indentation is made, is regarded as one of the SPMs widely used, together with the above-described various microscopes.
The scanning probe microscope can obtain surface information in a desired sample area through a mechanical probe while performing relative raster scanning or XY scanning with respect to the mechanical probe and the sample, thereby mapping the obtained information on a TV monitor. Further, an SNOM and the like can perform fine processing or optical information recording by causing a light beam emitted from an end of a mechanical probe to act on a workpiece. Furthermore, a nano-indentator can form irregularities on a sample surface to similarly perform fine processing or information recording.
In such a scanning probe microscope, a relative position along the Z axis of the sample and the probe, i.e., a distance between the sample and the probe is subjected to feedback control in such a manner that the interaction of the sample and the probe becomes constant during XY scanning. The movement along the Z axis is different from regular movement along the X axis and the Y axis but irregular in order to reflect the surface shape or surface state of the sample. The movement along the Z axis is generally referred to as Z scanning. The Z scanning has a highest frequency among those of XYZ scanning. A frequency of X scanning by the scanning probe microscope ranges from approximately 0.05 to 200 Hz, and a frequency of Y scanning corresponds to (the frequency of X scanning)/(Y scanning lines). A number of Y scanning lines is 10 to 1000. Furthermore, a frequency of Z scanning is approximately several-fold to 100-fold of pixels per one line of X scanning with respect to a frequency of X scanning.
For example, in order to fetch an image having 100 pixels along the X axis and 100 pixels along the Y axis in one second, a frequency of X scanning is 100 Hz; a frequency of Y scanning, 1 Hz; and a frequency of Z scanning is not less than 10 kHz. It is to be noted that a scanning frequency of this example is presently the highest scanning frequency for the scanning probe microscope, and the frequency of X scanning is usually approximately several Hz. The scanning unit must be stable against external vibrations, and vibrations generated from the scanning unit itself by the internal scanning operation must be suppressed in order to realize such a high scanning frequency as in this example.
The scanning unit is driven by vibrating a support portion supporting the scanning unit as a counteraction. The vibration of the support portion again acts on the scanning unit to vibrate an object. Therefore, the scanning unit requiring accurate positional control for the object must suppress the generation of such vibrations as much as possible. Although one effective method for suppressing the occurrence of vibrations is to slowly move the object, this goes against the necessity for repeatedly moving the object in a short period of time required in the scanning unit.
A main object of the present invention is to provide a scanning unit capable of suppressing generation of vibrations and thereby effecting accurate positional control.
Another object of the present invention is to provide a scanning microscope using such a scanning unit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.